Brake rebuild: Photo how-to guide: YZ400F

**The Stranger:Me** · 21st August 2009, 09:12

Originally Posted by motorbyclist

If you have any anti-seize I suggest you use it on the pad pin and caliper mounting bolts to save any future grief.

I know that using a torque wrench is heressy but at the risk of more derision I will mention it again.

I always use Loctite and a torque wrench on caliper mounting bolts. I have never had a loctited bolt seize upon removal.
I have known caliper bolts to fall out and brakes fail on 2 occasions (not my work). Both are on KB.
A torque wrench or loctite would have prevented this in either case. Anti seize wouldn't help one iota.

With a steel bolt and a steel nut/thread the bolt is designed to snap so as there is warning of a failure. This is a safety mechanism and is usually not available when a steel bolt is into an ali thread, as is often the case with caliper mounts. You may damage the fastener or the thread and be unaware of this. A torque wrench wont make you aware of it but it is likely to help prevent either of these in the first place.

I await the usual twaddle from the anti torque wrench brigade about how they just "know" when they have the correct torque etc - and look forward to more posts asking about heli coils and stripped sump plugs.

**motorbyclist** · 21st August 2009, 20:14

Originally Posted by renegade master

to pop the pistons out i just unblot the calipers take the pads out then pump the brakes to push out the pistons

MY method of removal is to pump the brake lever until both the pistons can be removed by hand.

so how is that different to what i did?

Originally Posted by DangerousBastard

A great read, and some useful tips for oldies and newbies alike. Nice work!

Observations ;

I have never replaced copper washers, and I have never had one leak.....

I wouldn't put water near any part of the process for any reason, unless you are going to bake everything dry afterwards.

cheers mate.

Now I have seen a washer leak, but never my own and i don't replace them either.

what do you use for cleaning then? Obviously i don't let water near them once i go to open them, but if they're meant to operate in wet conditions what harm does a good clean do?

Originally Posted by The Stranger

I know that using a torque wrench is heressy but at the risk of more derision I will mention it again......

I await the usual twaddle from the anti torque wrench brigade about how they just "know" when they have the correct torque etc - and look forward to more posts asking about heli coils and stripped sump plugs.

yeah I've threaded/sheared a few bolts in the past (including snapping a bolt on that very same set of brakes) and think a torque wrench is an essential tool, particularly for torquing engine heads/covers

And yes; loctite does prevent corrosion provided it's applied to the whole thread

**grotto** · 23rd October 2009, 09:55

I've never been able to just gently push the pistons back in. I've lubed the pistons and seals with brake fluid, and usually have tor resort to gentle pressure from a G clamp to get them back in.

Am I doing something wrong, or do others have the same problem?

**motorbyclist** · 25th October 2009, 14:19

which bikes? new seals shouldn't be that hard, but if they work fine who's to complain?

**NordieBoy** · 17th March 2011, 07:11

Just going through a caliper rebuild on the TT350.
Removing the pistons was... Interesting.
Only one would move with lever movement and then only reluctantly.
I ended up having to remove the caliper completely, drain it and use a grease gun on it which popped out the stubborn piston very easily.
Corrosion on the pistons and inside the caliper behind the seals.
The piston was hung up on the debris/gunk seen in the OP's pics which had hardened/compressed and had to be removed with a pick.

Now to steam clean the caliper, wait for a piston kit from Oz and buy a syringe.
I've already got a 1-way bleeder which is worth it's weight in myrrh.

**motorbyclist** · 17th March 2011, 17:34

Originally Posted by NordieBoy

Just going through a caliper rebuild on the TT350.
Removing the pistons was... Interesting.
Only one would move with lever movement and then only reluctantly.
I ended up having to remove the caliper completely, drain it and use a grease gun on it which popped out the stubborn piston very easily.

My yamaha manual said to use compressed air but also followed it up with about 2 pages of warnings

**NordieBoy** · 17th March 2011, 18:22

Originally Posted by motorbyclist

My yamaha manual said to use compressed air but also followed it up with about 2 pages of warnings

Compressed air didn't work. Not enough pressure

**CookMySock** · 18th March 2011, 09:59

Originally Posted by NordieBoy

Compressed air didn't work. Not enough pressure

Grease gun works good. Wear eye protection! 3000psi !

**NordieBoy** · 18th March 2011, 10:50

Originally Posted by DangerousBastard

Grease gun works good. Wear eye protection! 3000psi !

Nah, I'm good. Mine only goes to 1700psi

Little bro came around and cleaned up the pistons, seals and caliper. Rinsed the oil out with degreaser (no brake clean left), got rid of the degreaser with water, got rid of the water with petrol, got rid of the petrol with compressed air...

Bled the brakes using my 1-way bleeder and a pair of vice grips on the rubber line up near the M/C banjo to restrict the flow and give a bit of pressure to the lever and in less time than it takes me to flush new fluid through, it was all done!

I've got brakes!

One dust seal had a tiny nick but the rest were fine.

Looking at the pads and you can see they were wearing on an angle. One end is about 1mm thicker than the other.

**CookMySock** · 18th March 2011, 11:41

Shot. Yea bike brakes seem to need little cleanouts more than complete overhauls, with the seals still in good shape. I guess they don't do a lot of hard work compared to car brakes.

**NordieBoy** · 18th March 2011, 11:47

Originally Posted by DangerousBastard

Shot. Yea bike brakes seem to need little cleanouts more than complete overhauls, with the seals still in good shape. I guess they don't do a lot of hard work compared to car brakes.

We were quite surprised considering they'd not been touched since the bike rolled out of the factory 21 years ago.

**motorbyclist** · 18th March 2011, 16:19

Originally Posted by NordieBoy

Rinsed the oil out with degreaser (no brake clean left), got rid of the degreaser with water, got rid of the water with petrol, got rid of the petrol with compressed air...

wouldn't air/heat gotten rid of the water without leaving any of the petrol residue behind?